It is not possible by conventionally metallurgical processing (e.g. the mixing of borides and carbides into molten steel) to produce stainless steel alloys with high volume fractions of complex metal boron-carbides (CMBCs). Therefore, stainless steel based materials are typically softer and have inferior mechanical properties than non-stainless steels, e.g. tool steels.
U.S. Pat. No. 7,939,142 issued on May 10, 2011 to Blue, et al. entitled “In-Situ Composite Formation of Damage Tolerant Coatings Utilizing Laser” describes Fe-based amorphous compositions that are suitable for application as coatings on steel components. As long as the material remains in the amorphous state, it has superior corrosion resistance while maintaining excellent hardness that is especially desired under high wear applications. However, because amorphous materials are metastable by nature, the material eventually crystallizes, resulting in a decrease in corrosion resistance.
Previous research at Oak Ridge National Laboratory (ORNL) has shown that several compositions based on SAM 1651 and SAM 2×5 (described in U.S. Pat. No. 7,939,142) can be laser-fused to plain tool steel to increase the surface hardness and mitigate wear. Such coatings are beneficial to high wear applications where extended component lifetimes are not expected and under environments, which are not generally corrosive. However, for drilling operations such as those observed in geothermal applications, the corrosive environment has a severely pernicious effect on the coating integrity.